This R21 application (10 pages max) is being submitted in response to PA-03-015 "NHLBI Innovative Research Grant Program" which provides support for preliminary studies designed to demonstrate the feasibility of novel approaches using existing collections of human biological specimens. We propose to analyze an existing biochemical fraction that is a by-product of the sample preparation strategy described in the NHLBI-funded study (Pi-Michael Bristow) entitled "Genetic- Adrenergic Interactions in Myocardial Failure." The overall design strategy for the funded RO1 is to compare the gene expression between intact heart samples from nonfailing control subjects and subjects with biventricular failure from idiopathic dilated cardiomyopathy (IDCM), as well as a longitudinal, serial sampling study in IDCM subjects comparing treatments with beta-blockade to determine which adrenergic receptor pathway is responsible for changes in gene expression in the failing remodeled heart. The overall objective of this R21 proposal is to augment the microarray analysis with a parallel proteomic study. We propose to develop a quantitative proteomic strategy to analyze changes in protein levels from RNA-extracted biopsy- sized human heart samples and to determine the temporal changes in protein expression in the intact failing heart in response to beta-blockade. In Specific Aim 1, proteins and their modifications will be identified from samples taken from control subjects and subjects diagnosed with IDCM using Multi-dimensional Protein Identification Technology (MudPIT). In Specific Aim 2, differential expression of selected proteins and their modifications will be monitored from serial samples collected from patients during the course of beta- blockade treatment using quantitative proteomics. This proteomic study will further our understanding of the molecular mechanisms contributing to heart failure. By developing methods to analyze previously existing heart biopsy specimens, the redundancy of human studies will be significantly reduced.